This invention relates to a transportation system of a floated-carrier type and, in particular, a transportation system of a floated-carrier type including means for positioning the carrier exactly in a stop position.
To increase the degree of office or factory automation, transportation systems have recently been installed in some buildings. Such transportation systems are used to transport slips, documents, cash, samples, or the like, between a plurality of locations in the buildings.
In order to avoid spoiling the environment of the offices or the factories, the transportation systems of this system are expected to produce neither dust nor a high level of noise.
In one such conventional transportation system described in U.S. pat. appl. Ser. No. 726,975, now abandoned filed on Apr. 25, 1985, by inventors hereof, a carrier is magnetically suspended, in a non-contact manner, from a guide rail by means of an electromagnetic attractive force acting between the carrier and the rail, when the carrier is propelled along the rail. Generally, the carrier is either propelled, or braked, by causing the reaction plate mounted on the carrier to be energized by virtue of the stator of a linear induction motor.
In the transportation system it is required that, when the carrier is stopped in a predetermined stop position (station), it is positioned exactly at that location. This occurs in the situations where, for example, the cargo is loaded onto the carrier at the location of the station or the battery of the carrier is charged up. As such a positioning means use may be made of the following conventional means. As the first positioning means, at the stop position, a stopper means is provided which is actuated by a corresponding air cylinder and sandwiches the carrier. In this case, upon the arrival of the carrier, which is caused to coast along after the carrier has been slowed down by virtue of a stator, substantially at the stop position, it is sandwiched by the stopper means, so that the carrier is positioned exactly at the stop position. A second type of positioning means may be electromagnets, provided at the stop position an a guide rail, which position the carrier by magnetically attractive force between themselves and iron plate pasted on the carrier. A third positioning means is composed of two stators which are provided on both ends of the stop position in the direction of run of the carrier. In this case, the two stators are excited in the opposite direction each other so as to position the carrier in proper place. This type of positioning means is disclosed in Japanese Patent Disclosure (KOKAI) No. 57-3588 and Japanese Patent Publication (KOKOKU) No. 61-55338.
However, when the first positioning means is used, the transportation system cannot achieve its function that the carrier is magnetically suspended in a completely non-contact manner from guide rail. The second and third positioning means involves the problem of requiring large-sized equipment.